Commercial and military transport aircraft are typically designed to carry a given load of passengers, cargo or both, at a given range and/or at a given endurance. Occasionally, the range and/or endurance of the aircraft may need to be increased. Such extended range and/or endurance can be accomplished by installing additional or auxiliary fuel tank systems in the aircraft, typically by positioning fuel tanks physically within the aircraft's fuselage cargo space (i.e., that space within the aircraft's pressurized fuselage which is below the passenger deck). Conventional auxiliary fuel tank systems are typically comprised of additional fuel tanks and their respective equipment, manifolds, and harnesses necessary to manage the additional fuel carried in the tanks.
These additional fuel tanks and systems could come in diverse configurations, for example, with tanks installed under the wings, external to the aircraft or with tanks internal to the fuselage. These additional fuel tanks and systems could be configured to directly supply fuel to the engines or to transfer the fuel to other tanks and from there to feed the aircraft engines or be used to control aircraft center of gravity or even to transfer fuel to other aircraft, in flight or to other vehicles, on ground.
Whatever the reasons to install these additional tanks and systems, they should be at most practical to the aircraft operator. Thus, additional tanks and systems which complement an aircraft's main wing tanks should be relatively simple to install, remove, and integrate into the basic aircraft fuel system. One preferred auxiliary fuel tank system which is adapted to being positioned within the pressurized fuselage of an aircraft is disclosed in commonly owned U.S. patent application Ser. No. 11/637,922 filed on Dec. 13, 2006 (Atty. Dkt. No. 4439-11), the entire content of which is expressly incorporated hereinto by reference.
According to current aircraft certification requirements, auxiliary fuel tanks positioned within the pressurized fuselage must be of a double wall construction so as to provide enhanced protective barriers against fuel leakage. Any fuel which does in fact leak from the inner wall will find its way into the space between the walls and will be discharged outside the aircraft so as to prevent leaked fuel accumulation within the pressurized fuselage. The discharge point of the leaked fuel must also be visible to flight crew and ground personnel so as to provide evidence of a fuel leak from one of the on-board auxiliary fuel tanks. If leakage is detected, the aircraft would be grounded and would then require maintenance personnel to identify and fix the leaking auxiliary fuel tank before the aircraft could again resume flight operations.
Conventional leak detection systems provide for a drain port positioned generally in the center portion of an auxiliary fuel tank's bottom wall. Several problems ensue from such a center-positioned drain port. For example, since the drain port is located physically on the bottom wall of the auxiliary fuel tank, some space below the tank must be provided in order to accommodate the drain port fittings and drain tubing. Furthermore, this conventional center-positioned drain port may delay the time that fuel leakage is actually detected. That is, since the drain port is located in the center portion of the bottom tank wall, it is conceivable that certain aircraft attitudes may preclude fuel from actually reaching the drain port. As such, an increased quantity of leaked fuel would first need to be accumulated (with corresponding increased time) within the barrier wall space which would then be sufficient to flow into the drain port.
It would therefore be desirable if improvements could be made to auxiliary aircraft fuel tanks that would provide enhanced visual leak detection. It is towards providing such improvements that the present invention is directed.
In certain embodiments, auxiliary fuel tanks are provided having an inner barrier wall defining an interior volume for containing aircraft fuel, an outer barrier wall adjacent the inner barrier wall so as to define a space therebetween, and a drain part having a port in fluid communication with the space to allow leaked fuel within the space to be discharged therefrom. The drain part may be positioned at a corner junction between at least side and bottom walls of the outer barrier wall. In some advantageous embodiments, the drain part is positioned at a corner junction between at least two adjacent walls (e.g., the side and bottom walls), preferably three adjacent walls (e.g., the side, bottom wall and end walls) of the outer barrier wall.
One or more drain parts may be provided on each auxiliary aircraft fuel tank. If a plurality of drain parts are provided, then each drain part will preferably have a port in fluid communication with the space between the inner and outer barrier walls to allow leaked fuel within the space to be discharged therefrom, and each drain part will be positioned at respective corner junctions between at least side and bottom walls of the outer barrier wall, preferably between the side wall, the bottom wall and an end wall of the outer barrier wall.
Aircraft may thus be provided with one or more of such auxiliary fuel tanks.
Visual leak detection systems are also provided for auxiliary aircraft fuel tanks. In this regard, such visual leak detection systems will include an auxiliary aircraft fuel tank positioned within a pressurized space of an aircraft fuselage, the auxiliary aircraft fuel tank having an inner barrier wall defining an interior volume for containing aircraft fuel, an outer barrier wall adjacent the inner barrier wall so as to define a space therebetween, a drain part having a port in fluid communication with the space to allow leaked fuel within the space to be discharged therefrom, wherein the drain part is positioned at a corner junction between at least side and bottom walls of the outer barrier wall. A discharge manifold is provided so as to discharge leaked fuel exterior of the aircraft fuselage. Tubing fluid-connects the port of the drain part to the discharge manifold. In such a manner, leaked fuel is directed through the drain part from the space between the inner and outer barrier walls to the exterior of the aircraft where it may be visually detected. Again, one or more of such auxiliary fuel tanks may be provided within an aircraft's pressurized fuselage.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.